brorob
Posts: 104
Joined: Sat Oct 31, 2015 5:53 am

Regen braking can be dangerous on icy roads

Sat Dec 19, 2015 9:17 am

I'm posting this under the problems area of the forum because I think this safety concern should be addressed by BMW. Curious if others have experienced this.

Basically I had the rear end of my i3 "kick out" a few times yesterday while driving home on icy roads. This happened when slowing down for a stop sign when already driving slow. Freaked me out when this first happened but I was driving slow enough for the conditions to avoid the ditch and any vehicles. Had this happened on a multi-lane road, the rear end probably would have hit any car next to me. Fortunately this only happened a few times and I didn't hit any ditches, cars, or mailboxes.

I'm surprised that the BMW engineers didn't take this into consideration when engineering the aggressive regenerative braking system. I think it would be helpful (and safer) if there was a "snowflake button" that could be selected to either completely turn off the regenerative braking so only the brake pedal activates the brakes, or to significantly reduce the regen when taking your foot off the pedal. I would feel much safer driving the car in these conditions if this feature existed. The Volt has the option to change the regen level so I'm sure BMW could do the same.

This commute was a rare occurrence, probably the worst drive home since I've lived north of town for over 15 years. Roads were literally covered with ice and main highway (which I would have avoided) was closed. Every northbound road was backed up with cars either stopped or going 10-15 MPH. The commute that usually takes less than 30 minutes took about 2 hours. Unfortunately I can't afford a winter wheel set so I'm cautiously driving this winter on the all season tires. I did have less problems than some other vehicles driving up a few slight inclines in the icy conditions.

Anyone else experience this?

Off topic, I was able to conserve the battery by using the heated seats and keeping the cabin heater off, but I did have to turn on the defrost a few times to remove condensation from windows. I was happy that my range didn't change much after about an hour of stop and go traffic at night while using the heated seats and playing music fairly loud.

jadnashuanh
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Location: Nashua, NH USA

Re: Regen braking can be dangerous on icy roads

Sat Dec 19, 2015 11:45 am

YOu, as the driver, have ultimate control of the amount of regen used by the position of the accelerator pedal. It is not hard to coast or adjust the amount of regenerative braking to help avoid those situations.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV
Soon (hopefully!) A 2021 X5 45e will replace the above

i3an
Posts: 120
Joined: Tue Oct 14, 2014 1:09 pm
Location: San Francisco

Re: Regen braking can be dangerous on icy roads

Sat Dec 19, 2015 2:08 pm

I'm surprised to hear this. As once a motorcycle rider I learned (the hard way) to lean on the rear wheel brake first in slippery conditions, so as to anchor the back end and avoid fish-tailing, and I presume the i3 does the same as the regen works only on the rear wheels. Perhaps it is time to pony up for those winter tires.

Stevei3
Posts: 365
Joined: Mon Sep 02, 2013 9:02 am
Location: the Netherlands

Re: Regen braking can be dangerous on icy roads

Sat Dec 19, 2015 3:28 pm

Hi guys,
it has't been a problem for me when driving on normal wintery roads, even in mountainous areas (Switzerland, Austria), but I've noticed two things:

1) we were caught in 10 centimeters of new snow on 2000+ meters in the Swiss Alps on summer tires in june this year. This was not funny. Uphill was still sort of possible with help of the DSC system, but downhill was downright dangerous. It seems the stability-control 'needs' winter tires in snowy conditions.

2) for me, it's impossible to drive very slow (say 10 km/h, 6 mi/h) downhill on slippery roads. Sit rep: heavy snow, ca. 15 cm new snow on the road from our rented holiday-cottage in Austria. This time on the appropriate winter tires. Steep grade (say 10%), good tarmac road surface under the snow, road barely as wide as our car, very, very tight hairpins. The car wanted to rocket downhill at the slightest feathery touch of the accelerator, or wanted to stop due to regen when lifting a bit. This made a controlled, slow, confident descent impossible. The second time we had to negotiate the road, I had to put the car in 'N' and use the brakes to gain some sort of control.

Caveat: a 'snow' setting would be welcomed by me. Or the system has to be tweaked to perform better under the circumstances like #2

Regards, Steven

jadnashuanh
Posts: 5036
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: Regen braking can be dangerous on icy roads

Sat Dec 19, 2015 3:46 pm

People need to learn to feather the pedal a bit more carefully. It really isn't hard to go between accelerating, steady speed, coasting, and mild to full regen by the position of your foot - it's all about smoothness in your actions and a little finesse. This gets harder if you are switching between 'normal' cars (say an ICE) and the i3, but once you learn it, you'll have lots more control. Summer tires in the mountains with snow or ice can earn you a significant fine in much of Europe, and almost certain 100% liability should you be in an accident. Worst case, chains may be called for as well. BMWUSA choses not to import the OEM set to the states, but should be readily available in Europe. I guess I've been lucky, in my driving, I've only needed chains once to get me where I needed to go, but they probably would have been a safer choice a few other times as well.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV
Soon (hopefully!) A 2021 X5 45e will replace the above

alohart
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Location: Honolulu, HI

Re: Regen braking can be dangerous on icy roads

Sat Dec 19, 2015 7:55 pm

jadnashuanh wrote:YOu, as the driver, have ultimate control of the amount of regen used by the position of the accelerator pedal. It is not hard to coast or adjust the amount of regenerative braking to help avoid those situations.
If one is trying to coast to a stop but one's deceleration is insufficient, the additional regen when either lifting the accelerator pedal more or actually braking could cause a loss of rear wheel traction.

Years ago, I drove a school bus in Vail, Colorado. The bus had snow tires but no studs. Once, when the bus was empty, I was coasting in gear on a very icy downhill freeway offramp. Engine braking caused the rear wheels to lose traction. The only way I was able to regain control was to shift to neutral to eliminate the braking force from the rear wheels and then pump the brakes lightly to decelerate (no ABS back then).

So if I were driving an i3 on icy roads and lost rear wheel traction while decelerating, I'd do as Stevei3 did: shift to neutral to eliminate all regen braking and then use the brakes to decelerate (ABS should help).
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

TomMoloughney
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Re: Regen braking can be dangerous on icy roads

Sat Dec 19, 2015 8:10 pm

I've been driving BMW EV's since 2009 and have gone through six winters with them. The MINI-E in 2009-2011, the ActiveE 1012 to 2014 and the i3 from 2014 to now and have probably driven more than 20,000 miles in the snow and ice so I've had a bit of experience with this.

My take has been that the regenerative braking has actually made the cars perform better in icy conditions. By controlling the level of region, and mixing it in with a little friction braking, you can really keep the car in better control than with friction brakes alone. jadnashuanh said it correct about the driver being able to control the amount of region applied. If your going fast enough were you need to pull off the accelerator completely and abruptly, than you may be going too fast for ice covered roads in the first place. Now, emergencies to come up, and you need to stop quickly, but in my experience the traction control and ABS on the i3 seems to work pretty well with the regenerative brakes in preventing too much slippage.

The i3 does perform better in these situations than its predecessors and it seems BMW is getting it better and better as they have more experience with EVs and regenerative braking. One thing to note is that I do have dedicated winter tires. My i3 has the 20" sport wheels with the Summer-only tires so I really had no choice. I always recommend winter tires for any car that is exposed to snow, ice and a couple months a year of temperatures under 40 degrees. Winter tires make a huge difference. Even the best "All Season" (no season, really) can't compare with how much better winter tires perform in cold weather driving.
Tom Moloughney
MINI-E: (6/09 - 1/12)
BMW ActiveE: (1/12 - 5/14)
BMW i3 REx: (5/14- 6/17)
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My i3 Blog:
http://bmwi3.blogspot.com

Blue20
Posts: 186
Joined: Tue Jun 17, 2014 2:12 pm
Location: SAE Combo (CCS) Deadzone

Re: Regen braking can be dangerous on icy roads

Sat Dec 19, 2015 10:26 pm

I have snow tires and haven't had any problem with regen.

In fact, I quite like the regen, as it feels like engine braking in stick shift.

Stevei3
Posts: 365
Joined: Mon Sep 02, 2013 9:02 am
Location: the Netherlands

Re: Regen braking can be dangerous on icy roads

Sun Dec 20, 2015 2:03 am

Hi guys, Jim, Tom,

sorry to be on the defensive side here. I may not be an expert like Tom in winter E-driving, but I do have some experience in these circumstances (for a flatlander), also because I used to be an avid offroader, accustomed to deep mud (with ice underneath) and snowy conditions (picture Finland in winter).

I try to state two points, on the first we agree:

a bit of a moot point (duh!): winter tires are a must. Jim, you are correct that in Germany and Austria, winter tires with good thread are compulsory. Mind the thread: anything with less than 4mm is considered a summer tire in Austria! The fines for inappropriate rubber are *really* hefty (I think up to 50.000 euros), liability woes aside. When we were caught out in the snow (point 1), it was a freak snowdrift in june that surprised even the Swiss... It made for an interesting experience: the Ecopia summer tires, unlike Tom's 19 inchers in our case, perform terribly on snowy slopes. No brainer point made....

Over to the second point:

I agree with you that under normal winter driving conditions, the cars set-up is very good. It is easy to feather the E-throttle and control regen to drive very very 'softly', thereby never loosing traction. Also, DSC works perfectly here. But the case I made is that there has been a situation where I wanted to go so slow that normal driving parameters no longer seemed to count. The problem for me was not caused by loss of traction per se, but by the inability to maintain a slow, steady pace to the next hairpin. Upon lifting but a hair of the throttle, the back wheels wanted to lock-up. The descent was fairly long, so I had ample time to try to find the sweet spot of the throttle, but I wasn't able to find it. In our 4x4, we would have used the diesels engine braking in low-range first or second gear to keep the speed in the neighbourhood of a brisk walking pace. Granted, this was a situation where our 4x4 would have been better suited, but has anyone tried this with their i3? Recap: 3 km (2 mi) downhill, new snow, ~10% incline, hairpins barely wide enough even for i3's turning circle, winter tires.

BTW: switching to neutral on one occasion was a violation against my offroad lesson #1: never ever drive but one foot not in gear. I've seen interesting and potentially devastating accidents happen, for instance when one of our groups pickup popped out of gear on a 200 meter descent of ~25% in the Belgian forests...

Regards, Steven

brorob
Posts: 104
Joined: Sat Oct 31, 2015 5:53 am

Re: Regen braking can be dangerous on icy roads

Sun Dec 20, 2015 9:57 am

jadnashuanh wrote:YOu, as the driver, have ultimate control of the amount of regen used by the position of the accelerator pedal. It is not hard to coast or adjust the amount of regenerative braking to help avoid those situations.
While I agree with your comment (and others about not abruptly taking your foot off the accelerator), there are situations when this will be hard to avoid. When I had this happen I was coming to a stop sign at the bottom of a small icy hill. This was also my first time ever driving this car in snowy/icy conditions so my brain's natural response in this situation was to take my foot off the accelerator. I was caught off guard because of how fast this happened and I'm sure this will happen to others that either haven't driven the car in the snow/ice, need to come to a stop quickly, or don't have time to react quickly enough to find the sweet spot of the accelerator. I was able to prevent this for the rest of the icy drive being conscious of regen driving techniques, luckily no icy downhills.

My point with this thread is to point out that having the ability to turn off the regen braking would make some driving situations safer. And yes, driving without winter tires in the winter isn't ideal but not everyone can budget $1800 for an extra set of wheels for a leased vehicle.

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